llvm-dwarf-dump: include type name for AT_containing_type

Type attributes are currently printed as:
  DW_AT_type    (<address> "<name>")
For example:
  DW_AT_type    (0x00000086 "double")

However, containing_type attributes omit the name, for example:
  DW_AT_containing_type    (0x00000086)

In order to make the dwarf dumps easier to read, and to have consistency
between the type-like attributes, this commit changes the way
DW_AT_containing_type is printed so that it includes the name of the
type it refers to:
  DW_AT_containing_type    (0x00000086 "double")

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D127078